Platelet-rich plasma (PRP) is a blood-derived product that is rich in platelets. PRP is typically obtained from the blood of a patient and is used in regenerative medicine.
Platelets play a fundamental role in hemostasis and are a natural source of growth factors. The release of these growth factors is triggered by the activation of platelets that can be initiated by a variety of substances or stimuli such as thrombin, calcium chloride or collagen. Growth factors are naturally occurring proteins capable of stimulating cell proliferation and differentiation. Studies have found that growth factors are important in different stages of the wound-healing cascade and greatly influence mitogenic and cellular differentiation activities (Pierce et al., Proc Natl. Acad Sci. U.S.A. 86(7), 2229-2233 (1989) and J. Cell Biol. 109(1), 429-440 (1989) and D. L. Steed et al., Surg. Clin. North Am. 77, 575-586 (1997)). Therefore, growth factors are potentially useful for specifically promoting wound healing and tissue repair. PRP generally may include one or more of transforming growth factors (TGF), fibroblast growth factors (FGF), platelet-derived growth factors (PDGF), epidermal growth factors (EGF), vascular endothelial growth factors (VEGF), insulin-like growth factors (IGF), platelet-derived endothelial growth factors (PDEGF), platelet-derived angiogenesis factors (PDAF), platelet factors 4 (PF-4) and hepatocyte growth factors (HGF).
In particular, transforming growth factors (TGF) present in PRP specially include those of the TGF-β family. TGF-β is a protein that controls proliferation, differentiation, and other functions of cells. It can also act as a negative autocrine growth factor. TGF-β is known to activate fibroblasts to form procollagen resulting in collagen deposition within the wound. Other growth factors such as PDGF are activators of collagenase during wound healing allowing reshaping of collagen for wound strength.
PRP has many medical applications, primarily in constructive oral surgery and as part of a composition used as a surgical adhesive. PRP has been used to form a fibrin tissue adhesive through activation of the PRP using thrombin and calcium, which activate the platelets to release their contents such as cytokinins and other growth factors. For example, U.S. Pat. No. 6,322,785 discloses an autologous platelet gel comprising PRP for bone graft and dental implant applications.
The use of PRP has expanded into novel applications, such as bio-tissue engineering or autologous and allogenic tissue grafts, as well soft tissue regeneration (Oikarinen et al., Dent. Traumatol. 19, 19-29 (2003)). These applications include PRP as part of a composition for wound healing (U.S. Pat. No. 5,599,558) and tissue repair (U.S. Pat. No. 6,811,777), for use as a tissue sealant (U.S. Pat. No. 5,585,007) or in combination with a biopolymer to temporarily block arteries and veins (U.S. Pat. No. 5,614,204). Moreover, WO 2011/127071 relates to PRP formulations and their use in treating ischemic injury, particularly damaged connective tissue, cardiac tissue and lung tissue.
U.S. Pat. No. 6,811,777 discloses a platelet-rich plasma composition for treating injured tissue such as connective tissue, cardiac muscle, skeletal muscle, disc material, vertebral body, brain, spinal cord and vascular tissue by introducing the platelet-rich plasma composition into and around the site of a tissue injury.
The most expeditious source of PRP is from blood extracted from a patient, the PRP may thus be obtained and activated for use on the same patient; methods of using a patient's own blood are called “autologous” or “autogenic” donor methods. When the blood is donated by a human, but not the same human being treated, is called “homologous”. Homologous sources of PRP may be biologically or immunologically incompatible with the patient and can imply a potential risk of contamination with hepatitis and HIV contaminants. Autologous PRP has several safety advantages. For example, since PRP is generally a byproduct of the patient's own blood, disease transmission or immunological reactions are not an issue. However, patients with complex systemic diseases can affect the concentration of growth factors in their blood and in any of the blood-derived preparations, therefore will not benefit from the advantages of this type of treatments. Furthermore, certain treatments required platelet compositions which must be prepared on a daily basis and thus require regular blood withdrawal from the patient.
In view of the above, “heterologous” sources of PRP (from a foreign specie) may be of interest since they can provide a reliable, largely available and highly reproducible source of raw material. For example, porcine blood is less likely to carry a human viral infectious risk (HIV, hepatitis, etc), the production of growth factors is nearly 100% identical to their human counterparts and, is a source of efficient and constant concentration of growth factors. Additionally, in many countries, slaughter blood is discarded as waste material for lack of possibilities of using the blood.
Thus, it would be highly desirable to obtain composition comprising PRP without the need of a patient's own blood and from a more available, accessible and economical source such as porcine blood.
Furthermore, the use of autologous PRP for treating patients affected by knee degeneration with PRP intra-articular injections has been described by G. Filardo et al., Knee Surg. Sports Traumatol. Arthrosc. 19(4), 528-35 (2011). Osteoarthritis is a joint disease with a high incidence and prevalence in the population. The main symptom is pain, causing loss of ability and often stiffness. It has no cure and palliative treatments such as administration of analgesics and anti-inflammatories are mainly used to treat the symptoms. Indeed, sustained release of growth factors contained in PRP has preventive effects against osteoarthritis progression. The treatment with PRP injections can reduce pain and improve knee function and quality of life but with a short-term efficacy. These preventive effects appear to be due to stimulation of cartilage matrix metabolism caused by the growth factors contained in PRP (Saito et al., Clin. Exp. Rheumatol. 27(2), 201-7 (2009)).
PCT/IB2008/001916 discloses a method for the treatment of articular diseases or articular pain, which comprises the infiltration in the joint of a compound that comprises at least one autologous blood-derived substance.
As explained above, growth factors are known to be useful for promoting wound healing and tissue repair. The addition of exogenous growth factors to wound has been shown to increase the rate at which the wound is closed, the number of cells in the healing area, the growth of blood vessels and the strength of the scar (Carter et al., Biolog. and Clinical Implications 303 (1988)).
A platelet-derived wound healing formula in the form of a salve or ointment for topical application has been described by Knighton et al., Ann. Surg. 204, 322-330 (1986).
As disclosed in the above mentioned prior art, most biologicals, such as peptides and protein drugs, are currently used as parenteral formulations because of their poor oral bioavailability. The main reasons for the low oral bioavailability of biologicals are their unfavourable physicochemical properties, which include enzymatic degradation, poor intestinal membrane permeability and large molecular size (R. I. Mahato et al., Crit. Rev. Ther. Drug Carrier Syst. 20, 153-214 (2003) and J. H. Hamman et al., Bio Drugs 19, 165-177 (2005)). Platelet-rich plasma (PRP) contains high levels of biological entities, such as platelets and growth factors, therefore autologous PRP formulations are typically parenterally administered.
To date, there have been no reports of successful oral administration of PRP or successful use of heterologous PRP in vivo orally administered to develop the therapeutical effects described in the present invention.
The inventors of the present invention have surprisingly found that growth factor TGF-β1 is not degraded under gastric and gastrointestinal conditions and consequently TGF-β1 levels are not affected by digestion. This result was totally unexpected, especially in view of the poor oral bioavailability shown by biologicals.